Copy cat > /tmp/AdvLab03.java << 'JAVAEOF'
import java.util.*;
import java.util.function.*;
import java.lang.reflect.*;
public class AdvLab03 {
record Product(String name, double price) implements Comparable<Product> {
@Override public int compareTo(Product o) { return Double.compare(this.price, o.price); }
@Override public String toString() { return name + "($" + price + ")"; }
}
static class ImmutableList<T> implements Iterable<T> {
private final List<T> items;
ImmutableList(List<T> items) { this.items = List.copyOf(items); }
T get(int i) { return items.get(i); }
int size() { return items.size(); }
<R> ImmutableList<R> map(Function<T,R> fn) { return new ImmutableList<>(items.stream().map(fn).toList()); }
ImmutableList<T> filter(Predicate<T> pred) { return new ImmutableList<>(items.stream().filter(pred).toList()); }
@Override public Iterator<T> iterator() { return items.iterator(); }
@Override public String toString() { return items.toString(); }
}
record Pair<A, B>(A first, B second) {
static <T> Pair<T,T> of(T a, T b) { return new Pair<>(a, b); }
<C> Pair<A,C> mapSecond(Function<B,C> fn) { return new Pair<>(first, fn.apply(second)); }
}
// PECS: Producer Extends, Consumer Super
static double totalValue(List<? extends Number> nums) {
return nums.stream().mapToDouble(Number::doubleValue).sum(); }
static void fillPrices(List<? super Double> list, double start, int count) {
for (int i = 0; i < count; i++) list.add(start + i * 10.0); }
static <T extends Comparable<T>> T boundedMax(List<T> list, T ceiling) {
return list.stream().filter(e -> e.compareTo(ceiling) <= 0).max(Comparator.naturalOrder()).orElse(ceiling); }
static <T> void swap(List<T> list, int i, int j) {
T tmp = list.get(i); list.set(i, list.get(j)); list.set(j, tmp); }
public static void main(String[] args) throws Exception {
System.out.println("=== ImmutableList<T> ===");
var products = new ImmutableList<>(List.of(
new Product("Surface Pro", 864.0), new Product("Surface Pen", 49.99),
new Product("Office 365", 99.99), new Product("USB-C Hub", 29.99)));
System.out.println("names: " + products.map(Product::name));
System.out.println("prices: " + products.map(p -> p.price()));
System.out.println("expensive: " + products.filter(p -> p.price() > 100));
System.out.println("\n=== PECS Wildcards ===");
System.out.println("totalValue(ints): " + totalValue(List.of(864, 50, 100)));
System.out.println("totalValue(doubles): " + totalValue(List.of(864.0, 49.99)));
List<Number> dest = new ArrayList<>();
fillPrices(dest, 100.0, 5);
System.out.println("fillPrices: " + dest);
System.out.println("\n=== Bounded Max ===");
System.out.println("boundedMax (<=500): " + boundedMax(List.of(100, 500, 300, 800, 200), 500));
System.out.println("\n=== Generic Swap ===");
var list = new ArrayList<>(List.of("Surface Pro", "Surface Pen", "Office 365"));
System.out.println("before: " + list);
swap(list, 0, 2);
System.out.println("after: " + list);
System.out.println("\n=== Pair<A,B> ===");
var p = Pair.of("Surface Pro", 864.0);
var p2 = p.mapSecond(price -> "$" + String.format("%.2f", price));
System.out.println("pair: " + p);
System.out.println("mapped: " + p2);
System.out.println("\n=== Generic Comparable ===");
var prods = new ArrayList<>(List.of(
new Product("Surface Pro",864.0), new Product("Pen",49.99), new Product("Book",1299.0)));
Collections.sort(prods);
System.out.println("sorted: " + prods);
System.out.println("min: " + Collections.min(prods));
System.out.println("max: " + Collections.max(prods));
System.out.println("\n=== Type Erasure & Reflection ===");
var rawList = new ArrayList<String>();
System.out.println("Runtime class: " + rawList.getClass().getSimpleName());
System.out.println("Still ArrayList: " + (rawList instanceof ArrayList));
class Container { List<Product> products = new ArrayList<>(); }
var field = Container.class.getDeclaredField("products");
var genericType = (ParameterizedType) field.getGenericType();
System.out.println("Field: " + field.getType().getSimpleName());
System.out.println("Generic arg: " + genericType.getActualTypeArguments()[0].getTypeName());
System.out.println("\n=== PECS Summary ===");
List<Number> numbers = new ArrayList<>();
List<? extends Number> producer = List.of(1, 2.5, 3L);
List<? super Integer> consumer = numbers;
consumer.add(100); consumer.add(200);
System.out.println("Producer (extends): sum=" + producer.stream().mapToDouble(Number::doubleValue).sum());
System.out.println("Consumer (super): list=" + numbers);
}
}
JAVAEOF
docker run --rm -v /tmp/AdvLab03.java:/tmp/AdvLab03.java zchencow/innozverse-java:latest sh -c "javac /tmp/AdvLab03.java -d /tmp && java -cp /tmp AdvLab03" 